The Formation of the Anthocyan Pigments of Plants. 309 



on by oxydase, yield pigments. These reagents serve not only to demon- 

 strate the occurrence but also to determine the distribution of the oxydases 

 of the flower. By the application of the method it is found that the 

 distribution of oxydase coincides with that of anthocyan pigment. In 

 white flowers oxydase may be present in an active or an inhibited state. 

 In the former case some other part of the pigment-forming mechanism is 

 absent from the flower ; in the latter, the whole of that mechanism is present, 

 but its action is prevented by the inhibition of the oxydase. 



The present communication and that which follows (Part V) deal 

 primarily with the chromogens of the flower. 



Our first definite results demonstrating the existence of chromogens in 

 the flower and the relation of these colourless substances with the anthocyan 

 pigments were obtained with Brompton Stocks {Matthiola incana). These 

 plants occur in numerous colour-varieties, the chief of which are pink, red, 

 purple, and purple flaked with white. 



Flowers of any of these varieties, when treated with alcohol, lose their 

 colour rapidly. It is therefore easy to obtain a series of colourless petals 

 derived severally from each of the colour-varieties. 



If the decolorised petals of such a series be placed in water at room 

 temperature they begin almost at once to regain their colour, and, after a 

 quarter of an hour, each petal is found to be possessed of the identical 

 colour of the variety to which it belongs. The petal originally pink recovers 

 its pink colour, that from a red or purple variety becomes again red or 

 purple, and that from a white-striped purple variety reproduces with faithful 

 accuracy the purple and white pattern of the original. 



Despite the fact that our experiments have been carried out during the 

 winter months, when suitable material is somewhat scanty, we have been 

 able to prove that a similar recovery of natural colour is exhibited by many 

 other flowers, for example : — 



Aubretia, wallflower (Cruciferse). 

 Viola (Violaceae). 

 Pelargonium (Geraniaceae). 

 Cyclamen, polyanthus (Primulacese). 

 Begonia (Begoniaceae). 

 Azalea (Ericaceae). 

 Bilbergia (Bromeliaceae). 

 Dendrobium (Orchidaceae). 



Recovery of colour is shown also by the vegetative parts of plants which 

 contain anthocyan, for instance, the leaves of Fuchsia and Tradescantia, and 



